The present invention relates to a roughened printing plate support and also to a process and an arrangement for the production of this support.
For the production of printing plates, the metallic supports which are preferably comprised of aluminum or an alloy thereof, are usually roughened. According to the state of the art, roughening of such support sheets is carried out mechanically, for example, by grinding with an abrasive agent or by brushing; chemically, for example, using an acid; or electrochemically in electrolyte solutions. The prior art also discloses a combination of the abovedescribed processes. In the electrochemical roughening process, an asymmetrical alternating current or, preferably, a sinusoidal alternating current is, for example, employed and the electrolyte, e.g., hydrochloric acid or nitric acid, the concentration of the electrolyte, the current density, the temperature and other parameters can be varied, such that different surface structures are obtained.
However, the use of a sinusoidal alternating current does not produce optimum results with respect to current action and current yield, because the halfwaves are symmetrical.